Plant diseases are the cause of major economic losses in agriculture around the world (Martinelli et al., 2015). Viruses cause many diseases in plants of international importance and are responsible for great losses in terms of production and quality in crops; although difficult to calculate those economic losses those are considered to represent more than 30 billion dollars per year (Sastry and Zitter, 2014).
Viruses are strictly intra-cellular pathogens whereby their control is complicated and the main measures for their control are bound to destruction of infected plants or an excessive use of pesticides for the control of organisms that work like virus vectors (Nicaise, 2014). Antiviral compounds capable to cure viral diseases in plants practically are nonexistent and present control measures can only mitigate or prevent their occurrence (Gergerich and Dolja, 2006).
The first step required for handling viral diseases is the identification of virus. The strategy of subsequent handling will depend on the form by which a certain virus is introduced into any crop, how the virus is transmitted between the plants of the same crop, and how the virus survives in the absence of the crop (Haddidi et al., 1998). Some preventive measures include the use of virus-free certified seeds or vegetative organs, elimination of possible virus reservoirs in the surrounding wild vegetation and the modification of sowing and harvest practices. If the virus has any known transmission vector, vector control or exclusion is extremely important, for example: nematodes, insect and fungus vectors that can be controlled with nematicides, insecticides and fungicides, respectively (Gergerich and Dolja, 2006).
Nevertheless, an alternative for virus control may be found in own plant evolution which has provided resistance mechanisms through plant-virus interactions. In the last decades, processes for identification and understanding of phytohormone role and other key components in plant response to biotic stress have been developed (Robert-Seilaniantz et al., 2011). Starting from this idea, diverse natural origin ingredients may be selected to integrate an alternative to induce plant defense for virus damage through the activation of acquired systemic resistance mechanisms (Delaney et al., 1994).
Traditionally the use of diverse plant extracts with a number of applications has been described, being one of them product development with plant extracts allowing a favorable plant development, as well as resistance induction against diverse phytopathogens. Thus, several technologies have been described in the state-of-the-art, as described in international patent application WO 1989009200 A1 referred to the use of Viscum álbum or white mistletoe extract as part of a composition for soil conditioning and leaf fertilizer allowing nutrient restoring in soil and regeneration thereof. Moreover, the use of Viscum álbum extracts has been reported also in combination with other active compounds or extracts, such as in United States patent application No. 2014/0364309 A1 wherein Aloe vera and seaweed extracts are used to reduce damage in plants and their fruits caused by insects, parasites and other phytopathogens excluding virus.
International patent application WO2006097700 A1 refers to individual or combined use of plant essential oils such as eucalyptus (Eucalyptus globulus), spearmint (Mentha piperita), clove (Syzygium aromaticum) or marjoram (Lippia graveolens), in combination with vegetable oil and an emulsifier agent to improve plant growth. Similarly, several United States patent documents disclose the use of Coriandrum sativum extracts with a number of applications: the first one, U.S. Pat. No. 8,202,557 B, has been used to prepare insecticides, whereas in U.S. patent application 2006/0194698 A1 reference is made to active phytochemicals to protect plants from weeds, plagues and phytopathogens; and although antiviral properties for Coriandrum sativum extracts have been also described as in U.S. Pat. No. 8,529,968 B2, those have not been linked to phytopathogen virus.
On the other hand, in recent years and due to a demand of products allowing plant growth stimulation as well as increasing at the same time the protection spectrum against pathogens (virus, bacteria and fungi) a series of chemical compounds have been developed, as well as a new generation of products so-called bio-stimulants, which contains diverse substances and/or microorganisms which when applied to plants or the rhizosphere they improve crop development and biotic stress responses. Some bio-stimulants are described in international patent applications WO 2014020187 A1, WO 2013030422 A1 and WO 2012045189 A2 where in the first one bio-stimulants are prepared from mineral or animal origin compounds and seaweed extracts; in WO 2013030422 A1 patent application, residues coming from beer manufacturing for bio-stimulant production are used; whereas in WO 2012045189 A2 application, bio-stimulants are made from chitosan and Saccharomyces cerevisae hydrolysate.
Although a wide use of diverse plant extracts and plant essential oils with antiviral activity has been described, only a few have been tested directly on agricultural crops and specifically with phytopathogen virus.
Some other bio-stimulant products that are currently in market are made from glutathione, oligosaccharins and combinations of plant extracts and oils which provide certain effectiveness in fighting viruses, however none of them describes a combination of extracts and substances comprising present invention and which allow to have a synergistic effect for fighting DNA and RNA virus of higher impact on vegetable and fruit crop production. Some of the main technical advantages of the invention are as follows: prevention and reduction of virus damage, reduction of damaged plants, delay of appearance of virosis symptoms, a significant decrease in damage severity, a reduction of virus dissemination in the plantation, favoring the continuity of the plant growth and assures a higher yield under attack conditions.
In view of the state of the art background, the technical problem that solves the present invention is to provide a base formulation on the use of diverse plant extracts and plant essential oils to make a bio-stimulant action product for plant growth and development and phytopathogen virus inductive resistance, showing characteristics to be sustainable for safe application and for vertebrate and invertebrate health and environment low impact, which causes that present invention is novel, inventive and with a clear application in the field of agriculture.